For centuries, particle separation has been a process of great significance. Today, its importance spans across several fields ranging from medical diagnostics to wastewater treatment and water desalination. Some of the simplest separation techniques are sieving and filtration—processes that rely on membranes that allow certain particles to pass through while preventing the passage of others. Conventional membranes are porous and allow particles smaller than a typical pore size to pass through while retaining those larger than the pore size. Membranes that allow relatively large particles to pass through while retaining smaller ones, however, are counterintuitive and uncommon. While unusual in human practice, membranes with such capabilities are readily found in nature. Cells, for example, are encased by a phospholipid bilayer comprised of amphiphilic molecules that can dynamically reconfigure themselves. This property, in conjunction with other biological mechanisms, makes possible the engulfment of large particles without fluid exchange as exemplified by endocytosis.
As displayed in nature, membranes that allow large particles to pass while retaining small ones must be dynamically reconfigurable and self-healing—properties commonly exhibited by liquids. While liquids possess many unique materials properties, membrane engineering efforts have predominantly focused on solid-based materials. In recent years, the concept of incorporating liquids into solid-based materials has led to breakthrough surface technologies. For example, the incorporation of stable liquid layers into porous solids allows for self-healing, robust liquid-repellency, anti-biofouling, anti-icing, and even gating properties.
A number of references report use of liquid membranes or pseudo-liquid membranes for separating components based on the chemical attributes of such components. For example, articles to Naito and Li disclose use of polymeric membranes characterized as pseudo-liquids for separating components based on the chemical attributes of such components. See Naito et al., “Polymeric pseudo-liquid membranes from poly(2-ethylhexyl methacrylate)”, Polymer Journal, Vol. 41, No. 11. pp. 1005-1010, 2009; Li et al., “CO2 Separation from Flue Gas Using Polyvinyl—(Room Temperature Ionic Liquid)—Room Temperature Ionic Liquid Composite Membranes”, Ind. Bag. Chem. Res. 2011, 50, 9344-9353; U.S. Pat. No. 9,403,190 which discloses a liquid membrane with solid particles. However, a need still exists for separation of components that do not depend substantially on chemical attributes of the components.